Insulation additive drastically boosts performance of power lines
As we increasingly move toward renewable energy sources such as wind turbines, we're going to require the best means possible of relaying electricity from them to our cities. A new cable-insulating material may allow us to do so much more efficiently.
One of the problems with sending electricity through power lines is the fact that the farther the current has to travel, the greater the amount of energy it loses through those lines.
Increasing the voltage helps address this issue, but doing so requires the use of high voltage direct current (HVDC) cables. These have a limiting factor of their own, in that if the voltage is too high, the layer of insulating material within them may rupture.
In an effort to address this issue, scientists at Sweden's Chalmers University looked to a conjugated polymer known as poly(3-hexylthiophene) – or P3HT, for short. The material has previously been utilized in applications ranging from replacement retinas to cheaper and more efficient solar cells.
For the Chalmers study, P3HT was added to the polyethylene that's already used for insulation in HVDC cables, at a ratio of just five parts per million. When the resulting composite material was tested, it was found to have just one third the electrical conductivity of pure polyethylene insulation. And while other additives have previously been explored as a means of reducing conductivity, significantly larger amounts of them have been required.
Although more research is required, the results of the study suggest that HVDC cables incorporating P3HT in their insulation could withstand much higher voltages than is currently possible, further minimizing energy losses in the current they're carrying.
"Our hope is that this study can really open up a new field of research, inspiring other researchers to look into designing and optimizing plastics with advanced electrical properties for energy transport and storage applications," says the lead scientist, Prof. Christian Müller.
The research is described in a paper that was recently published in the journal Advanced Materials.
Source: Chalmers University
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There is also a benefit when switching AC power on an off. Because the AC power is passing through zero volts 120 times each second when you open a switch there is immediately a time with no voltage across that gap. When running a large DC load if you open a switch it will produce a large spark which takes some effort to contain.
However, very long AC lines act as radio antennas and they have issues with resonance and reactance which creates problems.
A high voltage DC signal is very simple. It is static. No radio waves. No resonances. No reactances to deal with. Really great. However, it is somewhat expensive to efficiently convert lower voltage to high voltage DC power and then at the destination change it back to lower voltage AC. Most HVDC lines are on the order of 300kV to 800kV. I found a reference to one using 1.1MV.
This is where the engineers go to work and calculate whether it is cost effective to use HVDC based on the distance and power involved.
Seems a like a very awkward way to describe an insulator. three times the resistance seems a better way to describe an insulator.